OK.........new guy here and been searching the threads. A lot of good information but some is confusing.
Like to get some good basic information to lead me in the right direction on my newly acquired 2009 KLX250S....
Want some performance upgrades.

1. Looking at the FMF Q4 exhaust. Good choice?
2. Do I need a new header pipe?
3. How do I know what jet kit to purchase for this exhaust? Recommendations?
Is this hard to do?.....I've tore apart carbs before, I assume it's pretty easy thing with the kit.
4. Can I leave the air box/filter alone?

Thanks for your help...

 

Lots of opinions out there...these are mine.


1. Looking at the FMF Q4 exhaust. Good choice?
Yes, they seem to be very popular for our KLX.

2. Do I need a new header pipe?
NEED? No. But an aftermarket (e.g. FMF powerbomb) supposedly improves low and mid range power.

3. How do I know what jet kit to purchase for this exhaust? Recommendations?
Is this hard to do?.....I've tore apart carbs before, I assume it's pretty easy thing with the kit.
Dynojet kits are very popular. I used the #2206, but there is another model for your 2009. The #2206 has a more aggressive needle, and should work just fine in the 2009 model, I believe. Getting the carb off is the hardest part of the job.

4. Can I leave the air box/filter alone?
Many of us open the air box up (remove snorkel, or lid, or replace the snorkel with a better flowing KDX200 snorkel) and install an aftermarket filter for improved air flow.

It's generally considered best to do the exhaust, air box, and jetting at the same time.

 

Welcome, I love the Q4, I would highly recommend the header too though. One word of caution, okay two, when you put the new exhaust on. Before you run it, check your airbox clearance, I had to pry mine out a little bit. I know others have melted theirs. Second, you will want to check into some flush mount turn signals for the rear, sooner or later, you will melt the right side one off. The jet kit is pretty straight forward. (just don't drill the brass plug) You'll want to at least take the snorkel off the air box too. Look around here as most guys have their upgrades listed. Have fun, they are great bikes.

 

One other note...if you KLX is hard starting like SO many of them are when cold, drilling out the enrichment (choke) jet to 0.018" is another thing to consider when in the carb.

 

I have the powercore4 which is the same exhaust just louder and I have had no issues with airbox or signals melting. But worth checking I guess. I have the 2010 model and I went with the dynojet kit for the klx300. Forget the part number

 

I don't necessarily have a cold start issue but rather once warmed up if I shut it down for a few minutes then it's hard to start. I have to mess with the choke/throttle to get it going.
Wonder if this is the same thing?
I assume a machine shop has to do this drilling??

I looked @ Motorcycle Superstore and see the "Dynojet - Stage 1 Jet Kit" for 2009 KLX250S so I assume this is what I want........no jet part number shown.

Thanks guys for all your comments......

 

Look on dynojet's site Dynojet Jet Kits - Offering Motorcycle Jet Kits & ATV Jet Kits
The one for the 300 mentioned above is the #2206, same one I and many others use. DJ lists the #2152 for the S, and 2156 for the SF. I'm pretty sure the #2206 will also work; some here say it may be better due to it's more aggressive needle, especially if you ever plan to go with a big bore mod.

You can drill the enrichment yourself. I did. But it is a very small bit, so you'll need a steady hand and a bit holder (not for the electric drill). Search the forum here for something like "0.018 enrichment" and you should find some "how to" threads. Do not use a 0.18" bit!

Opening up your fuel/air screw (which is probably covered with a plastic plug now) will richen up your pilot system and help some with warm starts. If it starts fine cold (and warm) with the choke on, drilling the enrichment jet probably isn't needed. On many of these bikes, even with the choke on, the bike is a bugger to start (that is, unless you know Deej's starting dance ).

 

Awesome information......

I looked at the PDF for install on the Dynojet website and it looks like a piece of cake. But the removal of the carb is probably the hard part, like you said.

Just got the bike last week...........2009 with only 180 miles on it. Basically a brand new bike for one heck of a deal on Craigslist.

Bike is at the local dealer now getting the recall done.......figured I'd get this out of the way before messing with any mods.

Thanks again for all the great information.

 

Good to hear it helps.
Here's a forum thread on carb removal. It's pretty good, but don't take everything there for gospel (e.g. the fuel screw is backed out 2.0 turns, not 20. and 2.0 turns is just a good starting point for further fine tuning. bla bla bla). Kawasaki KLX 250 slip on - HMF Engineering Forums